more robust system to deal with xorg.conf: broken xorg.conf files will be automatically restored to a configuration that works with hybrid graphics;

make sure that NVIDIA is always enabled on shutdown - this will avoid issues with the BIOS;

more.

nvidia-prime is a package that comes with a set of tools to enable Nvidia's Prime on MUXless systems.

Currently, nvidia-prime 0.5 is available in the Ubuntu 14.04 Trusty Tahr proposed repository and it will take a while before it's promoted to the main repositories.

2. Thanks to the latest nvidia-prime, we can also see a change in Nvidia Settings that landed about two weeks ago in Ubuntu 14.04 Trusty Tahr: an additional tab was added, allowing users to switch between GPUs:

This tab is only visible if nvidia-prime >= 0.5 is installed. After changing between the Nvidia and Intel GPUs, you'll need to log out or restart the system to apply the changes.

3. And finally, xorg-server was updated (version 1.14.4.901) with various Nvidia Optimus fixes, including a patch to fix GPU screen output hotplugging. Like the latest nvidia-prime, this update is only available in the Ubuntu Trusty proposed repository for now.

In my test under Ubuntu 14.04 LTS with these updates installed, I noticed some important improvements: there's no more screen / GTK theme corruption, my external monitor works out of the box (connected via a mini DisplayPort port that's hard-wired to the Intel graphics adapter; connecting a monitor via HDMI which is hard-wired to the Nvidia card doesn't work) and the temperature seems lower than in my previous experience with this under Ubuntu 13.10, although it's still a bit too hot for everyday use, at least with my laptop.

More Nvidia Optimus fixes will probably follow since Ubuntu 14.04 Trusty Tahr is in its early development stages and there are about four months until it's released.

If you want to try this out in Ubuntu 14.04, firstly enable the proposed repository (not recommended!) and then simply follow the instructions from HERE.